1. Field of Invention
This invention relates to polishing optical lens. Specifically, this invention concerns a new and improved apparatus for and method of polishing the surfaces of optical lens, using free-flowing polishing fluid pumped across and pressurizing a permeable membrane to conforms to the shape of the lens being polished.
2. Background Information
Prior art teaches several methods of and apparatuses for polishing optical lenses, however, these methods and apparatuses do not overcome many of the problems with lens polishing today. In fact, lens polishing methods have lagged far behind the rapid advances in lens cutting methods (e.g. programmable lathes). Today, much polishing work for custom lenses, which may have very complex curves, is still done by hand with lapping tools, in a very labor intensive manner. Some other problems in lens polishing are: a. the heat generated during polishing may warp or deform the shape of the lens, b. having to replenish the polishing compound during the polishing process, c. the cost of training personnel in polishing is both expensive and time consuming, d. lapping tools may grind the lens as well as polish them, and e. conforming the polishing surface to all shapes and curves of optical lenses.
Barnett (U.S. Pat. No. 3,471,976, "Process for Making Multi-focal Contact Lens") uses a chamois or other flexible material stretched across a bowl to selectively grind parts of the lens. Borish (U.S. Pat. No. 3,430,391, "Apparatus for and Method of Altering the Power of a Corneal Contact Lens") utilizes a resilient and deformable member having a polishing surface, with polishing compound on polishing surface, to alter the power of the lens. Barnett's patent and Borish's patent, however, are drawn to methods of grinding lenses, and not polishing. Both emphasize their methods as enabling one to change the shape of the lens in a desired manner. In addition, Barnett and Borish do not cool the lens during polishing, do not continuously replenish the polishing surface with polish, and do not teach the use of free-flowing polishing liquid across a permeable membrane.
Bank's patent (U.S. Pat. No. 4,373,991, "Methods and Apparatus for Polishing a Semiconductor Wafer") is directed at polishing--a method a polishing semiconductor wafers. Bank's invention pertains to the polishing of flat surfaces, such as silicon wafers. The polishing surface (pad) like the silicon wafer is flat and not conformable to a multitude of shapes. Furthermore, Bank's invention does not teach the use of free-flowing fluid pressurizing the polishing surface. The fluid of Bank's invention, instead, is used to create a "bearing" between the wafer and its holder, allowing the wafer to rotate while it is being polished. The fluid does not polish the wafer or replenish the polishing compound.
Rawston's patent (U.S. Pat. No. 3,050,909, "Apparatus for and Method of Polishing Aspheric Surfaces") and Barnett's patent (U.S. Pat. No. 4,458,454, "Methods of Shaping Contact Lens") teach the use of a sealed compartment, filled with air or liquid and covered by a flexible sheet of some sort, against which a lens is placed for polishing. In both cases the polishing compound is applied to the polishing side thereof, and is supported by fluid pressure from the other side. The potential problems, however, remain: a: the heat generated during polishing may alter the power of the lens, and b. having to reapply polishing compound during the polishing process. An additional concern to those schooled in the art may be the even application of the polish, which is not a concern in the applicant's invention.
Barnett's patent (U.S. Pat. No. 4,458,454) discusses the possibility of fluid compartment not being "fluid-tight", but rather that the fluid which "leaks" out could be replaced. This does not suggest, however, a free-flowing polish, nor a flowing fluid cooling the lens and replenishing the polish. Barnett (U.S. Pat. No. 4,458,454) does not suggest his flexible sheet should be intentionally permeable, only that it would not be a problem should some liquid accidentally leak out.
Houchin (U.S. Pat. No. 2,023,811) discloses a method of replenishing the polishing compound used in polishing, where the polishing compound is in fluid form and is applied onto a lap by a pan-like polish receiving and applying means. The polishing fluid, however, does not cross a conformable permeable membrane, does not pressurize the polishing surface (e.g. flexible permeable membrane) to conform to the shape and curves of the lens being polished, and is not applied directly and uniformly on the lens.
There is a need, therefore, for a method of and apparatus for polishing lens that overcomes the great variety of problems faced by lens polishers. Up to the point of this invention no polishing process has been established for polishing optical lens using free-flowing polishing fluid, pumped across a flexible, conformable permeable membrane, thereby: a. continuously replenishing the polishing compound, b. cooling the lens, thus, avoiding warping the lens during the polishing process, c. applying uniform pressure on the lens, d. conforming said flexible permeable membrane to all shapes (e.g. concave) and curves of lenses, e. polishing quickly and efficiently, and f. applying polish uniformly on the lens. Such a process, also, had not been suggested or taught in the prior art.